- 10.00: Trial lecture
- 12.00: Public defence
The ordinary opponents are:
- First opponent: Associate professor Evaggelia Papia, Malmö University, Sweden
- Second opponent: Associate Professor Hanna Tiainen, University of Oslo, Norway
- Leader of the evaluation committee: Professor Morten Nygård Bjørgen, OsloMet
The leader of the public defense is Head of Department Elin Holter Anthonisen, OsloMet.
The main supervisor is Senior Scientist Jan Tore Samuelsen, The Nordic Institute of Dental Materials (NIOM), Norway.
The co-supervisor is Professor Vigdis Aas, OsloMet.
Thesis abstract
Understanding the safety of dental materials: What happens when they’re in use
Dental devices such as crowns and bridges commonly contain metals, whereas dental splints are usually made of acrylic plastic. While they help restore function and comfort, these materials can release substances during use, including metal ions, chemicals from plastics, and microscopic wear particles. This raises important questions about their safety
What was studied?
This doctoral research focused on two key areas:
- Investigating how cobalt-chromium (Co-Cr) and palladium-silver (Pd-Ag) alloys release ions and how these ions affect human cells
- Exploring how different manufacturing methods (like 3D printing, milling, and autopolymerization) influence the physical and biological properties of acrylic-based bite devices.
To mimic real-life conditions, the alloy samples were tested under both static and dynamic settings, including simulated chewing. Human cells were exposed to extracts from these materials to assess cellular effects.
Key findings
Metal Alloys: Both Co-Cr and Pd-Ag alloys showed low ion release, even under simulated chewing. Only zinc and cobalt ions were harmful to the cells, but only at concentrations that are very high compared to clinical settings. Combining these ions with other alloy elements didn’t increase their toxic effect.
Acrylic Materials: Water solubility was lowest in the milled and the autopolymerized material, whereas one of the 3D-printed materials showed the highest water absorption and solubility of material components in water. Hardness was significantly lower in the 3D print materials, suggesting they may wear down faster.
Surface smoothness was achievable across all tested materials, helping reduce bacterial buildup. Biofilm formation (by Streptococcus mutans) was highest on the milled material. Cellular effects varied: some materials triggered the production of proteins linked to cellular protection, while others reduced cell viability. Prolonged water storage (12 h) of the autopolymerized material significantly improved biocompatibility.
Why It Matters and What’s Next?
Some substances used in these materials, like elemental cobalt and certain 3D printing chemicals, are classified by European regulators as Substances of Very High Concern (SVHCs). Understanding how these materials behave helps ensure they’re safe for long-term use in the mouth. Water storage may be a simple way to improve the biocompatibility of acrylic materials, thereby reducing the patient's exposure dose.
Future studies should test if this also applies to materials produced by digital methods. 3D-printed dental acrylic devices need further investigation, especially regarding wear resistance and bacterial growth. Researchers should also explore in more detail how printing methods and post-processing treatments affect performance and safety, in order to develop standardized workflow protocols for these materials.
